Slatted racks: everything you need to know

I was a newbee when my mentor took one look at my overcrowded, bearding colony and said, “I think you need a slatted rack.” And then he left.

Huh? What the heck was he talking about? And later, when I asked around, people who never used one told me they were worthless. After all, they assured me, if you needed one, it would have come with your beginner kit.

I have a tendency (more like a strict rule) not to listen to the overly-self confident, so I bought my first slatted rack and never looked back.

What is a slatted rack?

A slatted rack is an optional piece of beekeeping equipment that is often used in Langstroth hives. The rack (sometimes called a brood rack) is about two inches high and is placed between the bottom board and the lowest brood box.

The rack has the same outside dimensions as a standard Langstroth hive. The modern version has ten slats that run in the same direction as the frames in the brood box, with space between each one. In addition, it often has a 4-inch wide board that runs parallel to the front of the hive. You frequently see slatted racks in hobby hives but rarely in commercial hives.

What is the purpose of a slatted rack?

The purpose of a slatted rack is to provide dead air space
below the brood chamber. This layer of air helps to keep the colony cooler in
summer and warmer in winter.

To prevent developing brood from overheating in summer, honey bees are reluctant to accumulate in the nest. Instead, they may beard on the front of the hive or below the hive stand. However, if you add a slatted rack, the adult bees have a place to gather inside the hive without crowding the brood area. In addition, the extra space makes fanning easier and more efficient, which can improve ventilation and promote curing of your honey.

Some people believe that the purpose of a slatted rack is simply to reduce bearding. But others believe the extra space inside the hive can delay or reduce swarming by relieving overall congestion. Unfortunately, I have no statistics on either of these claims. Still, I love climbing under my hives on a hot day and watching all those bees congregate on the rack. They look happy! (Okay, scratch that, they look like bees.)

In winter, with entrances reduced and varroa boards in place, the slatted rack provides an insulating layer of air between the brood nest and the outside. It also moves the brood nest further from the cold and drafty hive entrance.

Any other advantages?

A queen may resist laying eggs close to the hive entrance, possibly because of fluctuations in air temperature. But by using a slatted rack to move the lowest combs further from the entrance, you can increase the amount of usable brood-raising space.

Is this a new invention?

Absolutely not. Back in 1900, Dr. C. C. Miller came up with the idea of providing a resting place for bees below the brood nest. This idea probably came from observing feral colonies. Bees in the wild attach their first combs to the top of their cavity and build down, adding more and more combs beneath the originals. Often the workers cluster on the very bottom, below the nest, in hot weather. The slatted rack gives hive-dwelling bees a similar opportunity.

Later, in about 1950, Carl Killion added the four-inch board along the front of the rack, apparently to reduce draftiness. But the guy who got all the credit for slatted racks was Richard F. Bovard of Honolulu. Bovard was a woodworker who devised an easy way to construct the rack as a one-piece unit, so for many years these were known as Bovard racks.

Which way do the slats go?

In the original design, the slats ran perpendicular to the brood frames. In fact, you still see these occasionally, except now we call these “horizontal slatted racks.” However, with the introduction of varroa mites and the common use of screened bottom boards, beekeepers wanted slats that ran parallel to the brood frames so mites could fall freely through the frames and the rack to the screen below.

This modern design is sometimes called a “vertical slatted rack.” You can buy them fully assembled for ten- and eight-frame equipment. My favorite one—no longer made—was a ten-frame version that came unassembled. It was cool because you could put in either 9 or 10 slats, depending on how many frames you used per brood box.

On the other hand, since screened bottom boards are not very good at eliminating varroa from a hive, I don’t think the alignment of slats and frames makes much difference. After all, slatted racks are not designed for varroa control. They are good at what they do but they can’t do everything.

Do all slatted racks have the horizontal board in front?

No. Some of the recent models leave that part out. The
purpose of the horizontal board was to reduce turbulence caused by air coming
through the entrance. It was also said to reduce the amount of light entering
the brood area, which the queen will shy away from.

Apparently it is cheaper to build a slatted rack without the
horizontal board, but if you want the full benefit from having a slatted rack,
I would look for one that has all the features.

When do you install the rack?

I always use a slatted rack, and I leave it in place all year long. I install it when I set up a new hive, even a nuc, and never take it out. In fact, some of the modern long Langstroths, such as the Valkyrie long hive, come with the slatted rack built in.

How do you tell the bottom from the top?

Good question. Newer ones are marked with something like “This side up.” That’s because zillions of beekeepers put them in upside down, which causes a horrendous mess when the bees fill it with comb. Unfortunately (I sheepishly admit) I know this from experience.

The top side is the shallow side. There should be bee space (about 3/8-inch) between the bottom of the brood frames and the top of the slats. If there is more space, the bees will fill it with comb, attaching it to the bottom of the brood frames and the inside of the slatted rack. Not good.

While we’re thinking about orientation, don’t forget that the four-inch wide board goes toward the front of the hive, near the opening. Slatted racks can be confusing at first, so pay attention.

Won’t bees build under the slatted rack?

Although I have never seen bees build under the rack, I suppose they could. With bees, things happen, which is why you have a hive tool.

Do you recommend slatted racks for everyone?

As I said earlier, they are optional. They add expense to a hive and they make it both taller and heavier. But I love them and consider them to be part of a normal set-up. Some beekeepers think slatted racks should be universally accepted as standard equipment, but sadly, they don’t come close. My recommendation is to try one and see how it works for you.

Build your own

One of my readers, David Manning of Sparta, Missouri, builds his own seriously good-looking slatted racks. If you are so inclined, read his post on How to build a slatted rack. Also, plans by another woodworking artist (and master draftsman), Matthew Waddington of Duvall, Washington, can be found here.

Otherwise, most bee supply companies sell slatted racks fully assembled. I usually paint the outside, before placing it above the bottom board, as shown below.

Your piece on slatted racks is very interesting; I’m a bit surprised they aren’t used more in the UK. Since I began beekeeping I have fitted canopies above my hive entrances to provide some shelter for the many bees which often “”hang out” on the alighting boards, sometimes even in heavy rain and I might try a slatted rack. I would have to custom-build it, though, as I use national hives, not Langstroth. Any tips?

Hi John, I made two up, they cost me about £9 each. As my hives are well positioned and warm-way I’ve left out the “apron” so as to permit maximum mite-drop. The slats are loose at present as I can’t be quite certain they’ll line up with the frames when I come to fit them. I asked my association whether anyone used them and got no response whatsoever!
I have the personal notes of a previous, now-deceased, local beekeeper; I will check for any mention.

I love the slatted racks and I have them on all my hives. I absolutely agree, they do build comb under it and extra caution should be taken when doing oxalic acid vaporization with the wand. In the photo you can see how I burned part of the comb with the wand.

Varroa boards. I guess they are like IPM boards. I live in Maryland and leave them out all year except when I vape and want to see the results. I have been told by someone who’s opinion I value highly not to leave them in. Forgot the reasoning but have not lost a hive over the winter for two years.

Rusty are you saying that you leave the screened bottom boards open all winter? Could you or have you done a piece on the pros and cons of solid bottom boards in winter vs open screened bottom board? If you use open screened bottom boards do you put in IPM boards to reduce the draft during cold spells and if so, below what temperature do you slip in the IPM boards?

I have done a lot of reading on this and as always there are so many differing opinions.

I generally leave the IPM boards out all winter. Sometimes, if the temperature drops into the 20s F for a week or more, I may slide them in. But as soon as it gets out of the 20s, I remove them. It all depends on your climate. Here where I live, moisture is the biggest problem, not cold. So doing what I do may not be best for you.

I know you wrote this specifically for me right? I don’t really believe that but your timing is perfect. I just placed my order with Mannlake and I will be putting slatted racks on my half of my hives. As always thank you for all the great information!! Whenever I have any questions about anything beekeeping related your blog is always one of my first searches.

I’ve used slatted racks now for a couple of years. I’ve always made my own except finally my beekeeping store started to make them because more than a couple of people have asked for them.

I bought a couple of theirs this year as I was in a hurry to set up a couple of hives. They are essential now to me. The next one I make I am going to add another horizontal board just at the edge of the bottom front lip. I’ve read the russians do this to help keep the wasps out. The narrow space they have to crawl through for a few inches allows the bees to attack them and drive them out. I just like making stuff as I don’t have any wasp issues now because I use fripinol to kill the wasp hive queens. A couple of drops in cat food wipes out all the pesky buggers!

My winter project this year is to make a 3 in one syrup feeder, candy board feeder and moisture quilt for the top once done syrup feeding. It will help get rid of a lot of excess spacers and reduce my plastic ziploc syrup feeder waste. Should be fun! I love beekeeping. All 7 hives in 3 different locations are doing great. Didn’t get much honey this year but all the bees are alive so that is most excellent.

My mentor said I didn’t need slatted racks, but the hives I inherited came with them so I kept them in place. I’m in Northern CA, where there’s been severe drought conditions for at least the last four years, and I swear those racks have helped sustain my colonies during the brutally hot conditions that have become the norm for my part of the country.

Great article! I have been making my own mortise and tenon slatted racks for years now. They are just as important as an outer cover and I would never consider having a hive without one. With all of the problems facing bees and beekeepers today, we must do everything possible to give these amazing creatures every advantage.

About 35 years ago when I was working for a commercial concern slatted racks were the current thing in the bee magazines and I ask my employer about what he thought of the idea. The spin on slatted racks at that time was they would limit swarming, which I would guess if they reduced congestion in the brood nest they should do to some degree. When I ask my employer what he thought of the idea his reply was “they seem to work after a fashion.” It seems he and his dad had tried them some 20 years prior to that date and some times they worked and sometimes they did not. It seem to me the larger message at the time that “everything old is new again.”

Beyond the above stated + of slatted rack they will also limit light at the very bottom of the frames which will encourage the queen to lay right up to the bottom bar. This is a good example of ‘marginal’ effect but X 10 frames would be a definite positive. This behavior is associated with the photo sensitive negative* characteristic of queens (which you can witness directly if you search for a queen and watch her actively move to the back side of the frame).

I was just wondering on the construction of the slatted rack if 9 bars would be the right construction method if you only run 9 frames in a 10 frame box?

*Another possible variable here is…. worker bees are photo sensitive negative until about the age of 12 days and then become photo sensitive positive after the age of 12 days.

I used slatted racks in 8 colonies 6 years ago. The bees built comb down from the bottom of the slatted racks on from 1 to 3 of the slats. As Ioana said, in such situations inserting a hot pan-type OA applicator into the bottom entrance is asking for trouble. Because of that (and despite changing over from pan-type to a ProVap), I stopped using them. But, truthfully, my colonies have never been better and I wonder how it is possible anyway to gauge whether or not the slatted racks are beneficial – simply by a reduction of bearding? Rhetorically speaking.

I’ve seen/heard a lot about these over the years. The only downside seems to be the initial cost. At least that’s the only thing I’ve heard the naysayers point to. Opponents claim they do nothing but cost money.

Their supporters claim they cure cancer and will bring peace to the middle east…etc.

Personally, I tend toward the middle in such debates. They may or may not live up to the claims but they aren’t hard to build and less than 20 bucks to buy. A small price to pay even if all it gives you is a little peace of mind. Seems rather silly to dismiss them without giving them a try. If they live up to any of their claims for *you,* it would be well worth such a small investment. If they do nothing at all, you haven’t lost a lot.

One might conclude that adding an additional drop wall to the horizontal front board , could actually cut drafts further – much like that double door you see in mall entrances, or larger buildings – to ‘gate’ the air circulation.
Also one key thing as shown here: https://en.wikipedia.org/wiki/Pelmet
Pelmets could also be used on the front of the hives – those could called (or akin) semi-enclosed awnings or entrances on “human buildings”. 🙂 In short, a really good idea for insulating hives from drafts – to create that dead air space.

Great article, Rusty and thank you and the others for the plans. I have 11 hives and only 1 has a slatted rack that a friend gave me. I thought I’d try it and it really does seem to create all the advantages you documented here. I’ll be making 10 more slatted racks this winter to install in the spring. Thanks for the many wonderful posts. You are one of my “go to” sources for outstanding, fact-based bee information. I believe I am a better beekeeper because of you!

I had to come back to this. I’ve been toying with this idea for quite a while. My idea is to put two rows of slates in a one inch shim with bee space between them. The idea is that this would solve the problem of burr comb while lowering congestion and drafts even more.

I’ve never gotten around to actually building one to try it but it seems feasible.

You mention a 3/8 gap between the bottom of the frames and the slats. If I’m doing a screen below the slats, how much distance do I give the bees below the slats? Hopefully I’m understanding how it works. Thank you.

No problem, John; I’m still not mobile but remembered I’d already taken the photos! The slats are loose for the moment, I’ll lock them in position (or perhaps allow the bees to do so!) when I can position them accurately below the frames that will hang over them so that mites can drop through unimpeded. Thanks for posting them Rusty!

I built 4 slatted racks and installed them last fall. An issue that evolved over winter was their interference with mite counts. It wasn’t until doing an oxalic acid treatment that the front board became an issue. I very quickly realized it would prevent some portion of mites (30% in a Warre Hive) from reaching the counting board. I like “data” so was never fully pleased with getting partial-results when doing mite counts after treatments. I will continue using them but plan to replace them with new racks absent of the front board. I’m not convinced the front board is entirely necessary in any event. Winter entrances are already reduced – mine are down to 1″ X 3/8″. That size reduction alone reduces wind. Add the slatted racks and you get further wind blockage. Bees in my hives wintered at the very top of the hives clustered clinging to quilts – the warmest spot in the hives. They were so far away from the lower entrance I can not see the addition of the 4″ board making any difference to the bees. My assessment is that part of a slatted rack is not needed. Better is having a rack that does not interfere with monitoring mites.

On the subject of mites, my mentor came back from a show last summer with a brilliant contraption, a set of copper tubing shaped and brased to fit onto a gas burner and accept a dosage of oxalic acid. Takes about 15 seconds and done. They get a bloody good dose too without having to seal up the openings as with the tablet heaters, also the price is very reasonable. If you’re interested I’ll send you the link.

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